JP2973472B2 - Plasma CVD equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming a thin film by a chemical vapor deposition method using plasma energy and a reactive gas, and an apparatus capable of forming a thin film having a uniform thickness and a three-dimensional shape. About.

[Prior Art] Conventionally, as shown in FIG.
A plasma CVD apparatus is known which is provided with a vertically extending reaction tube 2 and a substrate holder 3 provided at an intersection.

In this plasma CVD apparatus, a substrate 4 is placed on a substrate holder 3, a reaction gas is supplied from a gas supply source to a reaction tube 2, and a microwave is introduced into the waveguide 1, whereby a plasma is formed around the substrate 4. Is generated, and a reaction gas is decomposed by plasma around the substrate 4 to deposit a component of the reaction gas on the surface of the substrate 4 to form a thin film having a desired composition on the surface of the substrate 4.

As another example of the plasma CVD apparatus, as shown in FIG. 15, a horizontally held reaction tube 2 penetrates a vertically held waveguide 1, and a substrate holder 3 is provided at an intersection. Structured devices are also known.

[Problem to be Solved by the Invention] In the case where the plasma CVD apparatus having the above-described configuration is used, when a three-dimensional shape such as a dome is used as the substrate 4, as shown in FIG. Since the strong plasma 5 is generated, the reaction gas is thermally decomposed around the substrate 4 and deposited on the surface of the substrate 4, and as a result, a thin film 6 is deposited on the outer surface of the substrate 4 as shown in FIG.

However, when the film is formed by the plasma CVD apparatus having the above structure, the film thickness tends to be larger on the upper side of the substrate 4 and smaller on the lower side of the substrate 4. The film thickness ratio could be as high as 4: 1.

Then, a detailed study of the cause of the above-mentioned film thickness difference revealed that the relative positional relationship of strong plasma with respect to the substrate had an important effect on the formation of the thin film.

That is, when a film is to be formed on a three-dimensional substrate such as a dome, the effect of electron impact is weak when the distance to strong plasma is large, and the effect of electron impact is strong when the distance to strong plasma is small. As a result, the upper side of the base 4 becomes high temperature and the bottom side becomes low temperature, and the temperature distribution varies,
It is considered that this causes a change in the film thickness.

In the conventional CVD apparatus shown in FIGS. 14 and 15, the reaction tube 2 penetrates through the waveguide 1. Therefore, in order to prevent leakage of electromagnetic waves through the reaction tube 2, Tube 2
Has a disadvantage that it cannot be formed large.
There was a problem that large ones could not be used.

The present invention has been made to solve the above problems,
Even when a film is formed on a substrate using a three-dimensional substrate such as a dome, the variation in film thickness can be suppressed to within ± 10%, and a film can be formed on a large substrate. An object of the present invention is to provide a plasma CVD apparatus capable of forming a high-quality thin film with good reproducibility.

Means for Solving the Problems According to the invention described in claim 1, in order to solve the problems, a reaction tube connected to a reaction gas supply source and into which a reaction gas is introduced, and a reaction tube penetrating the reaction tube are provided. Plasma CVD comprising a microwave waveguide to be formed, and a substrate holder for setting a three-dimensional substrate at the intersection of the reaction tube and the waveguide.
An apparatus, wherein the substrate holder comprises a rotation axis for rotating the substrate, the central axis of the waveguide is provided to be inclined with respect to the central axis of the circuit axis of the substrate holder, and the substrate holder is rotated by the rotation of the substrate holder. The microwave waveguide is provided so as to be rotatable about a central axis of the shaft, and the microwave waveguide is generated in the reaction tube so that the plasma generated by the microwave waveguide can be freely generated in an inclined state with respect to the substrate. It is characterized by being inclined.

In order to solve the above problem, the invention described in claim 2 is a waveguide to which a microwave oscillator is connected, a reaction vessel provided to partition the inside of the waveguide, and an inside of the reaction vessel. 1. A plasma CVD apparatus comprising: a pump for reducing pressure; and a substrate holder provided in a reaction vessel for installing a three-dimensional substrate, wherein the substrate holder comprises a rotating shaft for rotating the substrate. , The central axis of the rotation axis of the substrate holder is provided to be inclined with respect to the central axis of the waveguide,
The substrate holder is provided so as to be rotatable around the central axis of the rotation axis of the substrate holder, and the plasma generated by the microwave waveguide is generated in the reaction tube so as to be tiltable with respect to the substrate. The microwave waveguide is inclined.

In order to solve the above problem, the invention according to claim 3 includes a reaction vessel having a reaction gas introduction pipe and an exhaust pipe connected thereto,
A plasma CVD apparatus comprising: a waveguide connected to a microwave oscillator; a decompression pump for depressurizing the inside of a reaction vessel; and a substrate holder provided in the reaction container and on which a three-dimensional substrate is placed. The waveguide has a two-part structure, and a waveguide connection hole is provided at a position on the opposite coaxial side of the reaction vessel, and the waveguide is connected to the waveguide connection hole. A microwave introduction window is provided at a connection portion between the wave tube and the reaction vessel, and the substrate holder includes a rotation axis for rotating the substrate, and a center axis of the rotation axis of the substrate holder is set with respect to a center axis of the waveguide. The substrate holder is provided so as to be rotatable around the central axis of the rotation axis of the substrate holder, and the plasma generated by the microwave waveguide in the reaction tube is inclined with respect to the substrate. The microwave is guided so that it can be freely generated. Characterized by comprising by tilting the tube.

"Operation" A plasma is generated along the length of the waveguide, and the strong part of the plasma at the center of the plasma is inclined with respect to the substrate. And the positional relationship between the strong part of the plasma and
The heating by the plasma becomes uniform on the substrate surface. Therefore, film formation proceeds on the surface of the substrate while the entire substrate is uniformly heated.

Also, when the reaction part is formed by partitioning the inside of the waveguide,
Unlike the conventional configuration where the reaction tube penetrates the waveguide, there is no problem of electromagnetic wave leakage, so the reaction part can be formed large,
A film can be formed on a large substrate.

Furthermore, if the waveguide is divided into two and connected to the reaction vessel, the size and shape of the reaction vessel are arbitrary, and a film can be formed on a larger substrate.

Embodiment FIG. 1 shows a first embodiment of the present invention, and a plasma CVD apparatus of this embodiment includes a reaction tube 1 provided vertically.
And a waveguide 11 penetrated through the central portion by the reaction tube 10 and provided at an angle to the reaction tube 10.

The intersection of the reaction tube 10 and the waveguide 11 forms a reaction vessel 16, and a base holder 12 is provided inside the reaction vessel 16. The substrate holder 12 is horizontally rotatably supported by a rotating shaft 14 provided vertically in the reaction tube 10.
The lower end of the rotating shaft 14 is connected to a driving device such as a motor (not shown), and the base device holder is started by starting the driving device.
12 is designed to rotate horizontally in the plane. Also,
The reaction tube 10 is connected to a reaction gas supply source (not shown) so that various reaction gases can be introduced into the reaction vessel 16.

The waveguide 11 is connected to a microwave generator (oscillator), and generates microwaves inside the waveguide 11 by introducing microwaves into the waveguide 11, thereby forming a substrate holder.
12 and its surroundings can be heated.

The waveguide 11 is provided so as to penetrate the reaction tube 10 in a state where the center axes of the waveguides 11 are inclined by about 45 ° with respect to the reaction tube 10, that is, in a state where the waveguides 11 are inclined with respect to the base holder 12. . Here, if the angle between the reaction tube 10 and the waveguide 11 is larger than 0 ° and smaller than 90 °, a free angle may be selected.

On the other hand, on the base holder 12, a base 15 having a hemispherical shape, a dome shape, or another three-dimensional three-dimensional shape is provided. As a constituent material of the base 15, it is preferable that a thin film formed on the surface is easily deposited, and it is preferable to select a material that facilitates separation of the thin film from the base 15 as needed after film formation. In order to separate the thin film from the base 15, a method of chemically dissolving and removing the base 15 or the like can be adopted.

Next, a case where a film is formed on the surface of the base 15 using the apparatus having the above-described configuration will be described.

Domed substrate on substrate holder 12 inside reaction vessel 16
15 is installed, and a reaction gas is introduced into the reaction vessel 16 from a gas supply source. Subsequently, plasma is generated in the reaction vessel 16 by a microwave oscillator. At this time, since the reaction tube 10 and the waveguide 11 are inclined, the plasma P is generated above the substrate 15 in an inclined state as shown in FIG. In this state, a film is formed while rotating the substrate holder 12 horizontally.

As shown in FIG. 2, when the substrate 15 is rotated while the plasma P is opposed to the substrate 15 in an inclined state, the entire substrate 15 is heated more uniformly than before. Here, the plasma P is applied from the top (one side) of the dome-shaped base 15 shown in FIG.
Is compared with the distance from the bottom (the other side) of the peripheral surface of the dome-shaped substrate 15 to the plasma P, the difference between them is that the conventional plasma 5 and the substrate 4 shown in FIG.
It becomes smaller than the case of. In other words, the difference between the distance from the apex portion of the base 4 of the conventional example shown in FIG. 16 to the plasma 5 and the distance from the bottom side portion of the base 4 to the plasma 5 in the conventional example shown in FIG. It becomes larger than the case. Therefore, if a film is formed in this state, a thin film having a uniform thickness is formed on the entire surface of the base 15.

FIG. 3 shows an apparatus according to a second embodiment of the present invention.
In the apparatus of this embodiment, the waveguide 11 is inclined with respect to the base holder 12 similarly to the above-described embodiment, and the reaction vessel 16
Is an example provided inside the waveguide 11.

Also in this embodiment, the waveguide 11 is
Is inclined, so that the same effect as the device of the first embodiment can be obtained.

FIG. 7 shows a device according to a third embodiment of the present invention. In the device of this example, 20 is a microwave oscillator, 21 is a waveguide connected to the oscillator 20,
Container walls 22, 22 made of quartz or the like are provided on a part of the waveguide 21.
To form a reaction vessel (reaction section) 23.

A gas introduction pipe 24 for connecting to a reaction gas supply source is connected to the reaction vessel 23 through the peripheral wall of the waveguide 21, and an exhaust pipe 26 for connecting to an exhaust pump 25 is also provided. It is connected through the peripheral wall of the wave tube 21. It is preferable that the gas introduction pipe 24 and the exhaust pipe 26 be as small as possible in diameter in order to reduce leakage of electromagnetic waves.

Further, a pipe 28 that penetrates the peripheral wall of the waveguide 21 in a state inclined with respect to the central axis of the waveguide 21 is connected to the reaction vessel 23, and a tip of the pipe 28 is connected to the reaction vessel 23. A rotating shaft 29 whose base end is put out of the reaction vessel 23 is inserted therethrough. The first end of the rotating shaft 29 is
The base holder 12 equivalent to that used in the embodiment is attached, and the base end side of the rotating shaft 29 is connected to the rotating shaft of the motor 30. Further, in order to prevent leakage of the electromagnetic wave from the waveguide 21, it is a matter of course to reduce the diameter of the pipe 28. In FIG. 7, reference numeral 31 denotes a plunger.

In the CVD apparatus having the configuration shown in FIG. 7, the substrate 15 is mounted on the substrate holder 12 in the same manner as the apparatus described above.
Is rotated to generate a plasma in the reaction vessel 23 and introduce a reaction gas, whereby a film can be formed on the substrate 15.

Also, in the apparatus of this embodiment, the rotation axis 29 is a waveguide.
Since it is inclined with respect to the central axis of 21, a thin film having a uniform thickness can be formed on the entire upper surface of the base 15. Further, in the apparatus of this embodiment, since the reaction vessel 23 is formed by partitioning the inside of the waveguide 21, even if the reaction vessel 23 is formed large, the problem of electromagnetic wave leakage unlike the conventional apparatus does not occur. Therefore, the reaction container 23 can be formed large, and a large substrate 15 can be formed in the reaction container 23. Further, since the rotating shaft 29 penetrating through the waveguide 21 can be formed shorter than the device of the first embodiment,
When rotating 15, the deviation caused by the swing of the rotating shaft is smaller than that of a long rotating shaft. Therefore, the base holder
The rotation state of 12 is stable, and the reproducibility when the film is repeatedly formed is improved.

FIG. 8 (a) shows an apparatus according to a fourth embodiment of the present invention. In the apparatus of this example, 31 indicates a waveguide connected to a microwave oscillator (not shown), and 33 indicates a reaction vessel (reaction unit). In the structure of this embodiment, the waveguides 31 are respectively connected to the waveguide connection holes provided on both side walls of the box-shaped reaction vessel 3, and the waveguide 31 is connected to the waveguide connection holes of the reaction vessel 33. A microwave introduction window 32 made of quartz or the like that enables a closed structure of the container 33 is provided. 34
Denotes a gas introduction pipe and 36 denotes an exhaust pipe.

In the apparatus of this embodiment, the same effect as that of the apparatus of the second embodiment can be obtained.

FIG. 8 (b) shows an apparatus according to a fifth embodiment of the present invention. In the apparatus of this example, 31 'indicates a waveguide connected to a microwave oscillator (not shown), and 33' indicates a reaction vessel (reaction section). In the structure of this embodiment, the waveguides 31 'are connected to the respective waveguide connection holes provided on the side walls of the cylindrical reaction vessel 33', and the waveguide connection holes of the reaction vessel 33 'are formed. A microwave introduction window 32 ′ made of quartz or the like, which is a part slightly distant from the inside and inside the waveguide 31 ′, enables the hermetic structure of the reaction vessel 33 to be provided.

In the apparatus of this embodiment, the same effect as that of the apparatus of the second embodiment can be obtained.

"Production Example 1" A diamond thin film was produced using a plasma CVD apparatus having a structure shown in FIG. 1 and having a tilt angle of 45 ° between a reaction tube and a waveguide.

As a plasma generating condition, the H ₂ gas into the reaction tube 200 cc /
And CH ₄ gas were introduced at an amount of 1 cc / min, the gas pressure was set to 50 Torr, and the power of microwave (2450 MHz) was set to 350 W.

A semi-spherical substrate with a radius of 10 mm made of single-crystal silicon was used as the substrate to be placed in the substrate holder in the reaction tube. By forming the film, a diamond thin film was formed on the substrate surface.

The hemispherical substrate on which the diamond thin film is formed is cut along a plane passing through the center of the bottom surface (circle) of the hemisphere, and the outer peripheral edge of the cut semicircular cross section (see the semicircle in FIG. 4). The film thickness of each part was measured. The results are shown in FIG. In FIG. 5, the angle α indicates the angle from the center of the semicircle of the cross section shown in FIG.

As is apparent from FIG. 5, a diamond thin film having a small thickness variation and a uniform thickness was formed by forming a diamond thin film on a substrate using the apparatus according to the present invention. The deviation of the film thickness was ±
It was within 10%.

On the other hand, FIG. 6 shows a case where a conventional plasma CVD apparatus formed by crossing a reaction tube and a waveguide at right angles is used, and a film is formed on the same substrate under the same film forming conditions as above, The results of measuring the thickness of the obtained thin film are shown.

In FIG. 6, the thickness ratio between the thickest part and the thinnest part was 4: 1.

From the above, by forming a film on a three-dimensional substrate using the apparatus according to the present invention, it is possible to obtain a deposited film having a film thickness variation within ± 10% and a film thickness more constant than before. It became clear that we could do it.

"Manufacturing Example 2 and Comparative Example" A reaction vessel (130 mm in length) having a structure shown in Fig. 7 and conforming to the waveguide standard WRT-2 was prepared, and placed between the plunger and the oscillator. After the plasma CVD apparatus was manufactured, a flat Si substrate (60 mm in diameter) was set in the reaction vessel, and the reaction vessel was evacuated to a vacuum by an exhaust pump.
Thereafter, a reaction gas obtained by mixing H ₂ gas and CH ₄ gas so that CH ₄ became 0.5% by volume was introduced into the reaction vessel, and the pressure in the reaction vessel was adjusted to 20 Torr.

Next, when a microwave of 2.45 GHz was applied by an oscillator, plasma was generated in almost the entire region of the reaction vessel. At that time, the temperature of the substrate surface was 800 ° C.
As described above, the temperature can be increased without using other auxiliary heating means. After filming for 100 hours in this state, Si
A diamond thin film could be formed on the substrate.

Fig. 11 shows the X-ray diffraction test results of the diamond thin film obtained as described above, and Fig. 12 shows the Raman spectroscopy results.
The measurement results obtained by (secondary ion mass spectrometry) are shown in FIG.

From the results shown in FIGS. 11 to 13, it was confirmed that a diamond thin film containing no impurities was formed on the entire surface of the substrate.

Next, a dome-shaped Si substrate (plane diameter 60 mm, height 16 mm)
Was placed in the reaction vessel of the plasma CVD apparatus so as to be inclined by 30 ° with respect to the traveling direction of the electromagnetic wave, plasma was generated under the same conditions as above, and a diamond thin film was formed on the substrate over 250 hours. At that time, the substrate was rotated at 50 rpm, and the temperature of the substrate surface was 850 ° C. ± 10 ° C. FIG. 9 shows the results of measuring the thickness of each part in the diamond thin film manufactured as described above. From FIG. 9, it has been clarified that a film having a uniform thickness can be formed on a dome-shaped substrate by the apparatus of the present invention.

For comparison, a conventional apparatus having the configuration shown in FIG. 10 was used to form a film on a dome-shaped substrate having an outer diameter of 25 mm and made of the same material as the Si substrate. In the apparatus shown in FIG. 10, 40 is a microwave oscillator, 41 is a waveguide, and 42 is a waveguide.
A reaction tube provided through 41, 43 is a motor, 44 is a rotary shaft 45 is an exhaust device, 46 is a base, and 47 is a plunger.

As a result of forming a film using the apparatus having the above-described configuration and using the same reaction gas under the same plasma generation conditions as described above, a diamond thin film could be formed. 1) is the result shown by the chain line in FIG. 9, and it was found that the film thickness was not uniform. In addition,
While the apparatus shown in FIG. 10 can process a dome-shaped substrate having a maximum diameter of 40 mm, the apparatus of the present invention shown in FIG. 7 can process a dome-shaped substrate having a diameter of 60 mm.

By the way, using the apparatus of the third embodiment, a diamond thin film was formed under the same conditions as above except that the substrate was inclined by 90 ° with respect to the microwave direction.
In this case, the film thickness distribution of the diamond thin film (Comparative Example 2) was as shown by the one-dot chain line in FIG. 9, and it was found that the film thickness fluctuated.

Therefore, from the above results, it was clarified that the film thickness distribution can be averaged by inclining the angle of the base with respect to the direction of the microwave.

Note that a film is formed on a dome-shaped substrate by the plasma CVD apparatus having the above-described configuration, and a dome-shaped structure made of a film-like body is obtained by, for example, chemically dissolving and removing the substrate after film formation. This structure can be used as a diaphragm of a speaker or the like. In this case, a dome-shaped speaker diaphragm having a uniform film thickness can be obtained.

[Effect of the Invention] As described above, according to the present invention, the waveguide can be provided to be inclined with respect to the rotation axis for rotating the substrate holder that supports the substrate, and the plasma can be generated in an inclined state with respect to the substrate. As a result, the difference between the distance between one side of the base and the plasma and the distance between the other side of the base and the plasma is equalized as compared with the conventional apparatus, so that the base is heated uniformly by rotating the base holder. be able to. Therefore, when the reaction gas supplied to the reaction tube is decomposed by plasma and deposited on the substrate, a thin film can be deposited more uniformly on the entire surface of the substrate than before. Therefore, there is an effect that a deposited film having a very small variation in film thickness within ± 10% can be obtained.

Further, if the reaction vessel is formed inside the waveguide, the problem of microwave leakage does not occur as compared with the conventional apparatus in which the reaction pipe penetrates the waveguide, so that the reaction vessel can be formed large. become able to. For this reason, it becomes possible to form a film on a substrate larger than before.

On the other hand, if the waveguide is divided into two and connected to the reaction vessel, the size and shape of the reaction vessel can be arbitrarily set, so that the reaction vessel can be made large. . For this reason, it becomes possible to form a film on a substrate larger than before.

[Brief description of the drawings]

FIG. 1 is a side view showing an apparatus according to a first embodiment of the present invention, FIG. 2 is an explanatory view showing a positional relationship between a substrate of the apparatus and plasma, and FIG. 3 is an apparatus according to a second embodiment of the present invention. FIG. 4 is an explanatory view showing the position (angle) at which the film thickness was measured, FIG. 5 is a graph showing the thickness distribution of a thin film manufactured by the apparatus of the first embodiment, and FIG. FIG. 7 is a graph showing a thickness distribution of a thin film manufactured by the apparatus, FIG. 7 is a configuration diagram showing an apparatus of a third embodiment of the present invention, and FIG. 8 (a) is an apparatus of a fourth embodiment of the present invention. FIG. 8 (b) is a block diagram showing an apparatus of a fifth embodiment of the present invention, FIG. 9 is a graph showing a thickness distribution of thin films manufactured by the apparatus of the third embodiment and a conventional apparatus, FIG. 10 is a block diagram showing another example of the conventional device, FIG. 11 is an X-ray diffraction diagram of the diamond thin film, and FIG. FIG. 13 is a graph showing the result of SIMS measurement of a diamond thin film, FIG. 14 is a configuration diagram showing an example of a conventional CVD device, FIG. 15 is a configuration diagram showing another example of a conventional CVD device, FIG. The figure shows the relationship between the plasma and the substrate in the CVD apparatus having the configuration shown in FIG. 14. FIG. 17 is a cross-sectional view of the thin film formed on the substrate. 10 ... reaction tube (reaction part), 11 waveguide, 12 ... substrate holder, 14 ... rotating shaft, 15 ... substrate, 16 ... reaction vessel, P ...
... Plasma, 20 ... Oscillator, 21 ... Waveguide, 22 ... Container wall, 23 ... Reaction vessel (reaction part), 24 ... Introduction pipe, 25 ...
Exhaust pump, 26 ... Exhaust pipe, 28 ... Pipe, 29 ... Rotary shaft, 30 ... Motor, 31, 31 '... Waveguide, 32, 32' ... Microwave introduction window, 33, 33 ' ... Reaction part.

Claims (3)

(57) [Claims] A reaction tube connected to a reaction gas supply source and into which a reaction gas is introduced, a microwave waveguide penetrating the reaction tube, and an intersection of the reaction tube and the waveguide. What is claimed is: 1. A plasma CVD apparatus comprising: a substrate holder on which a three-dimensionally shaped substrate is placed; wherein the substrate holder includes a rotating shaft for rotating the substrate;
The central axis of the waveguide is provided to be inclined with respect to the central axis of the circuit axis of the substrate holder, and the substrate holder is rotatably provided around the central axis of the rotation axis of the substrate holder. A plasma CVD apparatus characterized in that the microwave waveguide is inclined so that plasma generated by the waveguide can be freely generated in an inclined state with respect to the substrate. 2. A waveguide to which a microwave oscillator is connected, a reaction vessel provided for partitioning the inside of the waveguide, a pump for reducing the pressure inside the reaction vessel, and a pump provided in the reaction vessel. A plasma CVD apparatus comprising: a substrate holder on which a substrate having a three-dimensional shape is placed; wherein the substrate holder includes a rotating shaft for rotating the substrate;
The center axis of the rotation axis of the base holder is provided to be inclined with respect to the center axis of the waveguide, and the base holder is rotatably provided around the center axis of the rotation axis of the base holder. A plasma CVD apparatus characterized in that the microwave waveguide is inclined so that plasma generated by the microwave waveguide can be freely generated in an inclined state with respect to the substrate. 3. A reaction vessel to which a reaction gas introduction pipe and an exhaust pipe are connected, a waveguide to which a microwave oscillator is connected, a decompression pump for depressurizing the inside of the reaction vessel, and a pump provided in the reaction vessel. A plasma CVD apparatus comprising: a substrate holder on which a three-dimensional substrate is placed; wherein the waveguide has a two-part structure, and a waveguide connection hole is provided at a position on the opposite coaxial side of the reaction vessel. Is provided, a waveguide is connected to the waveguide connection hole, a microwave introduction window is provided at a connection portion between the waveguide and the reaction vessel, and the substrate holder includes a rotating shaft for rotating the substrate. The central axis of the rotation axis of the substrate holder is provided to be inclined with respect to the central axis of the waveguide, and the substrate holder is provided so as to be rotatable around the central axis of the rotation axis of the substrate holder. The plasma generated by the microwave waveguide is A plasma CVD apparatus characterized in that the microwave waveguide is inclined so that it can be generated in an inclined state with respect to a substrate.